The excitement seems to have been prompted by the performance of Rexam's credit default swaps. These derivatives give the owner insurance against a debt default by the company, and their value has risen sharply in recent days. Market professionals pointed out that Marks & Spencer's credit default swaps soared in a similar way before Philip Green's private-equity-type offer for the group last year.

A private-equity bid for Rexam will see the group's balance sheet loaded with debt, making a default by the company more likely and insurance against such an eventuality more valuable.

Analysts argued that the can maker's impressive cash flows could certainly support a private-equity-type bid for the company. But they also said that Rexam might be planning a major debt-financed acquisition, which would also explain the sudden rise in the price of its credit default swaps.

By the close of business, Rexam was the second best-performing blue-chip stock in London. Cairn Energy, 90p higher at 1850p, was the best. The Scotland-based oil and gas explorer was boosted by suggestions that its Indian oil assets may contain more crude than first thought.

Elsewhere in the sector, Dana Petroleum fell 40p to 855p after the group raised £34m through a placing of new shares at 870p. Dana will use the cash to fund its recently acquired assets in Algeria. An intense period of exploration activity is on the way at the group. Analysts expect Dana to dig six exploration and appraisal wells in the next four months.

The FTSE 100 index lost 16.3 points to close at 5,423.5. Nevertheless, Deutsche Bank suggested there are good times ahead for equity investors. The German broker raised its year-end target for the FTSE 100 to 5,600 from 5,500, and set a 2006 target of 6,000, which is 10 per cent more than current levels. Deutsche favours the retail, banking and oil sectors. Of the three it believes retail is most oversold and advised its clients to start building positions in this part of the market.

Meanwhile, Hays dropped 2.5p to 118.75p on talk UBS had sold 48 million shares in the recruitment group at 118.5p on behalf of an institutional client. J Sainsbury added 7p to 291.25p as dealers reported whispers that Brandes is looking to add to its shareholding in the supermarkets group. At the latest count, the US fund manager controlled 12 per cent of the company. Woolworths built on its recent gains, adding a further 1.25p to 35.25p, as a growing number of punters piled into the retailer, convinced that it is about to receive a bid approach.

Intertek was boosted in the morning by hopes the group will not remain as an independent entity for much longer, but lost ground in the afternoon as word spread that Credit Suisse First Boston had downgraded the stock to "neutral" from "outperform". Although the broker admitted that a bid for Intertek from its Swiss rival SGS would make sense, it pointed out that a spokesman for Intertek was recently quoted as saying the company knew of no reason for the strong jump in its shares over the past few weeks. Intertek closed 3p higher at 749p, having traded at 767p at one point during the day.

At the small-cap end of the market, BTG ticked 3.5p higher to 218.5p after reporting substantially reduced first-half pre-tax losses. Market professionals said Louise Makin, its new chief executive, has done well to boost royalty revenues and cut costs. Vane Minerals rose 0.75p to 12.75p, thanks to a bullish update from its copper prospect in Mexico.

Finally, Game gave up a further 1.75p to 82.75p on rumours Sony may apply a patent to its PlayStation 3 games that will prevent them from being played on any other console than the one on which they are first run. Sony's technology will allow an authentication code to be read and then rendered unreadable on other machines.

If true, this will be very bad news for Game. The retailer makes a large portion of its profits by selling second-hand computer games and consoles. Analysts estimate that second-hand software and hardware accounts for between 15 and 20 per cent of Game's shelf space.

Some analysts were sceptical that Sony would introduce such a measure. They said that it could backfire on the Japanese group because if implemented it is likely to reduce purchases of new games. In many, these are funded by consumers trading in old games in return for discounts on new releases.